High Pressure Pasteurization or High Pressure Processing (HPP) is a post-packaging treatment that eradicates food pathogens and spoilage organisms in food products. This process is also known as high hydrostatic processing (HHP) and ultra-high pressure processing (UHP). The key food sectors for HPP are ready-to-eat, whole muscle and sliced meats; seafood; fresh-cut fruit, juices, and smoothies; as well as deli salads, condiments, dips, soups, salsas, and sauces. Currently, premium salads such as pastas with protein that are made without preservatives have an average shelf-life of just four to eight days. HPP treatment can extend the shelf-life to thirty to fifty days while producing a product with a clean label for which consumers are willing to pay a premium price.
Pressure inactivates most vegetative bacteria at pressures above 60,000 pounds per square inch (psi). During HPP, foods are subjected to isostatic or hydrostatic pressure, which is equal from all directions, at levels up to 100,000 psi. This high pressure destroys pathogenic microorganisms by interrupting their cellular function. Within a living bacteria cell, many pressure sensitive processes such as protein functions, enzyme action and cellular membrane function are affected by high pressure with the result that the bacteria is unable to survive. In contrast, macromolecules in food that are responsible for flavor, order, and nutrition are typically not changed by pressure. HPP can be conducted at ambient or refrigerated temperatures, thereby eliminating thermally-induced off-flavors. The technology is especially beneficial for heat-sensitive products.
HPP is gaining in popularity within the food industry because of its ability to inactivate pathogenic microorganisms with minimal to no heat treatment, resulting in nearly complete retention of the nutritional and sensory characteristics of fresh food. Unique advantages of HPP include the following, for example: pressure transmission is instantaneous and uniform, is not controlled by product size, and is effective throughout the entirely of the food item. Other advantages of HPP over traditional thermal processing include reduced process time; minimal heat damage problems; retention of freshness, flavor, texture, color and nutrients; and reduction or elimination of the need for preservatives such as sodium.
In a typical HPP process, the product is packaged in a flexible container (usually a pouch or plastic bottle) and is loaded into a high pressure chamber filled with a pressure-transmitting (hydraulic) fluid. The hydraulic fluid (normally water) in the chamber is pressurized with a pump, and this pressure is transmitted through the package and into the food itself. Pressure is applied for a specific time, usually three to five minutes. The processed product is then removed and stored or distributed in a conventional manner. Because the pressure is transmitted uniformly (in all directions simultaneously), foods retains its shape, even at extreme pressures. HPP can be used to process both liquid and solid foods. The food to be processed must contain water and must not have internal air pockets. Food materials containing entrapped air such as strawberries or marshmallows would be crushed under high-pressure treatment, and dry solids do not have sufficient moisture to make HPP effective for bacterial destruction.
In general, HPP can provide a shelf-life similar to thermal pasteurization. For foods where thermal pasteurization is not an option—due to flavor, texture or color changes—HPP can extend the shelf-life many times compared to a non-pasteurized counterpart, thereby improving food safety. High pressure has very little effect on low molecular weight compounds such as flavor compounds, vitamins, and pigments compared to thermal processes. Accordingly, the quality of HPP pasteurized food is very similar to that of fresh food products and any quality degradation is typically influenced more by subsequent storage and distribution rather than the pressure treatment itself. Pressure also provides a unique opportunity to create and control novel food textures in protein-based or starch-based foods. In some cases, pressure can be used to form protein gels and increase viscosity without losing heat.
Prior to processing, packaged foods are typically loaded into a vessel such as carrier 10 shown in FIG. 1. A typical carrier has a diameter of about 14.5 inches and length of about 35.0 inches. A typical carrier 10 includes top openings 12 through which the packaged food products may be inserted into and removed from carrier 10. Packed food products may also be inserted and removed through either of removable ends 14. Ends 14 typically include a plurality of ports 16 through which water may enter and exit carrier 10. Moreover, an end 14 may include a direction indicator such as an arrow-shaped port 18, which assists an operator in proper orientation of the carrier 10 during processing so that the packaged food items do not fall out of openings 12 due to gravity. A single fully loaded carrier 10 can weigh up to about three hundred pounds. Carrier 10 can accommodate variously shaped packages, including bottles, cups and shrink-wrapped packages.
Because a filled HPP carrier 10 is very heavy, loading and unloading many filled HPP carriers into a high pressure pasteurization machine is a physically demanding job. Moreover, HPP carriers must be handled carefully, as scratches may compromise the strength of carriers and their ability to withstand the pressurization process. Thus, there is a need for an apparatus to assist an operator in moving loaded HPP carriers while protecting the carriers from potential damage.